So Corrie was almost Florrie – Florizel Street, after Prince Florizel. But a cleaner called Agnes at Granada TV said Florizel Street sounded like a disinfectant (does it, Agnes?), so they changed it to Coronation Street. This was the second time Agnes had saved what would become Britain's longest-running soap opera. It was because she was instantly spellbound by the pilot while clearing away the tea things from the producer's office that he knew it was a winner.

Is that true, I wonder? Did Agnes even exist? It doesn't really matter. What matters is that Harry Elton, the Canadian producer, decided to fight the Granada TV executives – who couldn't understand the appeal of a drama about the ordinary lives of ordinary people and were about to pull the plug on the whole thing – with everything he had. Guess what, he won.

The Road to Coronation Street (BBC4) chronicles the birth of a monster, 50 years ago this December. Yes, BBC4 – it's funny that the BBC should be celebrating a rival's birthday so fondly. And scheduling it so it doesn't clash with its subject matter – obviously a lot of the people who want to watch this are the same people who want to know what's currently going on in the Rover's Return. Very magnanimous, I'm sure. The Road to Coronation Street is fond, and warm, and charming, with a fine lead performance from David Dawson as cocky young writer Tony Warren. There are fine performances wherever you look, though some of them take a little getting your head around. So former EastEnder Jessie Wallace plays Pat Phoenix, who played Elsie Tanner. Lynda Baron is Violet Carson, who was Ena Sharples. And James Roache plays his own father, William Roache, who was – and still is – Ken Barlow. "It's only a week, what harm can that do?" he says. A week! James's father has now, by my calculations, been Ken Barlow for 64% of his life, and that's going up the whole time. Imagine it!

There's also a fine performance from Steven Berkoff as television baron Sidney Bernstein, who initially saw Tony Warren's script not as Hitchcock said drama should be – "life with the boring bits left out" – but pretty much the opposite. "What your writer seems to have done," he tells Harry Elton, "is to pick up all the boring bits and strung them together one after another."

Sydney changed his tune a bit later, though. It took Coronation Street about three months to reach No 1 in the ratings. There's nothing boring about 15 million viewers and a 75% audience share. I wonder if BKB – boring Ken Barlow – was boring, even then?

It's amazing that it was filmed live in the early days – or at least one of its two weekly slots was. So if the cat went missing just before Eric Spear's mournful trumpet sounded out over the Weatherfield rooftops, then that was it – no cat. There must have been an immediacy and a theatricality about it – the feeling that Pat and Violet and even boring William were doing it then and there, in your living room, for you – which maybe doesn't exist in the soap any more.

So what is going on today, 50 years on, in Coronation Street (ITV1)? The police take Gary in to the station to question him about an assault (it would be virtually impossible to do this one live, with all the location changes). That could mean going back behind bars. Behind the bar at the Rover's, Kylie's got her hand in the till. Sly Owen's got his hands in all sorts of metaphorical tills, mainly of the female variety, if you know what I'm saying. And Nick is dead excited about Natasha's scan, even though the one he's looking at, and showing everyone else, isn't hers, because she terminated her pregnancy, as everyone except Nick knows. You couldn't really accuse it of being all the boring bits strung together – or reflecting the ordinary lives of ordinary people.

Oh, and there's no sign of boring Ken in this one. But recently in the Street he's been joined by a long-lost son, who himself has a son. And Ken's new son and grandson are played by William Roache's real-life sons, Linus and James. So James is playing his dad on BBC4 and his dad's grandson on ITV. Got it?